1. Field of the Invention
The disclosure pertains to video reproduction devices and more particularly, to systems and methods for improving the sound of an audio/video signal whose picture frequency fluctuates.
2. Description of the Related Art
Analog video cassette recorders are film recording and reproduction appliances that are widely used at present. A problem with video cassette recorders stems from the control of the running speed of the magnetic tape which may vary by +/−10%. With a new video recorder and a magnetic tape in good condition, the range of variation is not as big and the variations compensate for one another over the duration of a film. When the video recorder is worn and/or the tape is damaged (too old), the range of variation increases and the variations may no longer compensate for one another. Such a variation in speed slows down or accelerates the picture rate and the sound band. While viewing, the drift of the picture is righted through line and frame synchronization information. If the drift of the band is too big, the picture may “jump”, that is to say from time to time a picture is lost or doubled up. The sound rate is also slowed down or accelerated, thereby decreasing or increasing the sound frequency. Moreover, the fluctuation in the running speed causes a phenomenon of “wow” on the sound, which is rather unpleasant to the ear.
Analog video recorders are products approaching the end of their life. They are currently being replaced with digital players/recorders. Digital players/recorders have the particular feature of storing the sound and the pictures in the form of coded digital data allowing superior sound and picture quality to that of analog video recorders while ensuring constant quality of reproduction independent of wear to the medium and/or the player.